Ground plane

I heared from many RF people that it is better when implementing RF Circuits on PCB to Make A ground plane ? i 've 2 Questions :-

1- Why The GND plane is used , i want to know more details ?

2- How can it be implemented , I think that Double sided PCB is used such that one side is used for routing layer and other side is a fully copper side and the componets is soldered in the routing layer only and no connection from any component to GND plane except the GND Nodes of the circuit , Is that is correct , I hope someone Assure of that ?

Hi

Unwanted couplings between traces are less if groun plane is used. EMI is less.
There are a lot of trace models to predict trace effect in such configuration---(You will see effects from traces inductances and capacitances at freq>~50 MHz)

In comon case the design on two layer pcb is more predictable at RF.

I think so.
Regards

Also it gives you a handy place to connect pins of IC's that are labelled "ground".

i heard that put vias beside the rf line can reduce the trace inductances and capacitances, did it really? is there some rules of put the vias?

I think the main point here is that the ground plane, the pcb dielectric and the trace line, all these components combine to form a microstrip line. The wave travels through this microstrip in quasi-TEM mode, as explained by many text books. If no ground plane existed, we can imagine the trace line can simply be an antenna.

br

vias along rf line become necessary when the frequency goes higher, especially in ultra-broadband system.

hi
i have a nice full article completely explaining the different gnd planes in MW circuits.
by the way,
using vias to hold the hexagonal protrusions can form a high impedance surface which is a PerfectMagneticConductor instead of Perfect Electric Conductor and can eliminate surface waves.

tell me to send it if you liked.

Hi,

I have a little question?
If I using in my design with microstrip,
To get Zo=50Ω: H=32mil, T=1.41mil=1oz, w=58mil, FR4 => ε=4.5

What is intresting me how much I must to move from microstrip so I wan't get CPW (Coplanar Wave Guide).
I know that minimum is height of PCB (in my case 32mil),
But my colleague say that at least 2*width (2w)

Who is telling the truth?

David